1. Field of the invention
The present invention relates to a multilevel image display method, and more specifically to a method and system for displaying a multilevel image by using a binary display apparatus.
2. Description of related art
Drive circuits for two-dimensional display panels such as plasma display panels, liquid crystal display panels, and LED (light emitting diode) display panels are constructed to selectively drive, on the basis of a given display data, a plurality of row electrodes and a plurality of column electrodes which are arranged orthogonal to each other.
FIG. 1 shows a block diagram of one conventional typical drive circuit for the two-dimensional display panel. The shown circuit includes a shift register 10 having a serial input connected to a data input port 12 so that a display data D is serially inputted through the input port 12 to the shift register 10 in synchronism with a clock pulse CK, so that the display data corresponding to one horizontal line or row is accumulated in the shift register 10. The shift register 12 having parallel outputs connected to a latch circuit 14, so that the display data of one horizontal line or row accumulated in the shift register 10 is transferred in parallel to and latched by the latch circuit 14 in synchronism with a horizontal scan or synchronism signal Hs and held in the latch circuit 14 during each one horizontal scan period. Each bit of the latch circuit 14 is connected to an input of a corresponding column driver 16, which applies or does not apply a voltage to a corresponding column electrodes 18 of a display panel 20 in accordance with a binary value held in the corresponding bit of the latch circuit 14.
The shown drive circuit also includes a row signal generator 22 connected to receive the horizontal scan or synchronism signal Hs and having a plurality of parallel outputs, which are connected through row drivers 24 to corresponding row electrodes 26 of the display panel 20. Thus, the row signal generator 22 responds to the horizontal scan or synchronism signal Hs so as to selectively activate only one of the parallel outputs for each one horizontal scan period so that only the row driver connected to the activated output of the row signal generator 22 applies a voltage to the corresponding one row electrode.
With the arrangement as mentioned above, display data D is inputted through the input port 12 to the shift register 10 in synchronism with the clock pulse CK so that the display data D corresponding to one horizontal scan period or line is accumulated in the shift register 10. The accumulated display data of one horizontal scan line is latched to the latch circuit 14 in synchronism with the horizontal scan signal Hs. For a next horizontal scan period, each of the column drivers 16 connected to the latch circuit 14 applies a voltage corresponding to the binary value held in the corresponding bit of the latch circuit 14, to the corresponding column electrode 18 of the display panel. On the other hand, the row signal generator 22 sequentially activates the row electrodes through the row drivers 24, one electrode by one electrode, in synchronism with the horizontal scan signal Hs. As a result, of intersecting points 28 between the activated row electrode 26 and all the column electrodes 18, intersecting points on column electrodes corresponding to binary display data of "1" is fired by a potential difference between the voltage applied to the column electrodes and the voltage applied to the activated row electrode. However, intersecting points on column electrodes corresponding to binary display data of "0" is not fired since these intersecting points are applied with only the voltage applied to the activated row electrode. Thus, an image is indicated on the display panel in accordance with the input display data D.
In the above mentioned display system, however, the display panel is of the binary display type so that each intersecting point (display pixel or dot) between the row electrodes and the column electrodes is simply fired in an ON/OFF manner by the associated drivers in accordance with the input display data. In other words, it is not possible to modify the brightness of the display pixel or dot, and therefore, a displayed image or picture having a multilevel brightness cannot be obtained.